The Ultimate HellBlazer Index is a site dedicated to tracking down all the appearences of John Constantine, the coolest comic character since Punisher Wolverine Batman. He’s cool with a "u" rather than with a "kew".
A link on that site points to a "definitive" site for Twilight, the legendary lost Alan Moore DC comics superhero crossover proposal, which links to the text of the proposal and features art drawn by past Alan Moore collaborators in the spirit of the series.